Unidirectional clutch pulleys of automobile alternators (generators) have been widely used in some high-end automobiles all over the world. When a generator is driven by a crankshaft of an automotive engine via a belt, a pulley unit, etc., excessive torque and tension may be exerted on the pulley, the rotating shaft (the axle) and the pulley as a result of cycling of induction, compression, combustion and expansion, and exhaust strokes. When the rotation of the crankshaft suddenly decelerates, since the rotating shaft of the generator has a large inertia, the belt is pulled in the direction of torque rotation producing a change in the tension, which may result in overload of the belt and thereby shortening its service life.
In the prior art, there is an OAD (overrunning alternator decoupler) spring friction unidirectional coupling damping generator (alternator) pulley, which can reduce the above-described overload produced in the belt by the change in rotation by using spring friction unidirectional coupling to interrupt the power or by deforming a torsion coil spring in an elastic fashion to change the torque, as disclosed in Chinese patent applications No. 200880128290.0 and No. 201020519051.2. It can filter both high speed and low speed vibrations. However, at present, an OAD with such a structure has the following technical problems: 1. one end of the friction spring is fixed on a retainer, which presses said end of the friction spring into a straight section so that a bending point forms between the straight section and the coil section of the spring. Frictional force will focus on this bending point. When friction clutching occurs in the generator due to high and low speed rotations, the bending point at the end of the friction spring, where it is fixed to the retainer, is prone to breakage. 2. In addition, the bending point and the outer circular surface of the friction spring are both used in braking and overrunning to generate friction with the inner diameter of the pulley hub. This not only results in short service life, but also requires complex manufacture process and high costs.